Evidence of Fibrinogen Breakdown by Leukocyte Enzymes in a Patient with Acute Promyelocytic Leukemia

On daunomycin treatment of a patient with promyelocytic leukemia, leukocyte elastase appeared in large amounts in the patient's blood. Also, the plasma fibrinogen was found to be partially degraded to early, X-like, fibrinogen degradation products. These early fibrinogen fragments were isolated and showed a low anticoagulant activity in a thrombin time test. Early fibrinogen degradation products, produced with leukocyte elastase in vitro, have a similar low anticoagulant activity. In contrast, plasmic degradation products inhibit clotting of fibrinogen to a large extent. Although alpha 2-antiplasmin and plasminogen levels were low, antithrombin III levels were not decreased. The low anticoagulant activity of the isolated fibrinogen fragments, the presence of elastase activity in the plasma--both immunological and amidolytic--and the normal levels of antithrombin III suggest that granulocytic enzymes, whose release was enhanced by the cytostatic treatment, were responsible for degradation of fibrinogen in this patient.